Learn Hardcore Turkish: Parkta koşarken güvenlik yeleği takmak faydalıdır. - It is useful to wear a safety vest while running in the park.

Koşarken is an adverbial participle (zarf -fiil) meaning “while running.” You form it by adding the suffix -ken to the verb root koş- (to run). Phonetic adaptation gives you koş-ar-ken → koşarken, which conveys that two actions happen at the same time.

Why is Parkta used instead of just park?

Parkta is the locative case of park, meaning “in the park.” Turkish marks locations with -ta/-te (after a consonant) or -da/-de, following vowel harmony. So park → park-ta tells us where the running takes place.

Why doesn’t güvenlik yeleği take the accusative -yi ending here?

In Turkish, a direct object is marked with the accusative -ı/-i/-u/-ü only when it’s definite or specific. Here güvenlik yeleği (a safety vest) is indefinite/general, so it stays in the nominative form. If you meant “the safety vest,” you’d say güvenlik yeleğini takmak.

What’s the role of takmak versus using giymek?

Giymek generally means “to wear” (clothing). Takmak is used for items you strap on, attach, or put on accessories—glasses, watches, helmets, and yes, safety vests. So takmak fits because a safety vest is strapped on, not slipped on like a T-shirt.

What does faydalıdır mean, and how is it formed?

Faydalıdır means “it is useful.” It comes from the adjective faydalı (useful) plus the copula suffix -dır/-dir. In written/formal Turkish, -dır completes the predicate, indicating a general truth.
• faydalı (useful)
• faydalı + dır → faydalıdır (it is useful)

Can you omit the -dır in faydalıdır?

Yes, especially in everyday speech you might just say faydalı, as in
Parkta koşarken güvenlik yeleği takmak faydalı.
However, dropping -dır makes it more informal and can sound like you’re simply listing things rather than stating a general rule or advice.

Why is the sentence built around takmak faydalıdır instead of “You should wear a safety vest”?

Turkish often uses an infinitive phrase as the subject of “it is + adjective” to give general advice or statements. The structure is:
[Infinitive phrase] + [adjective + -dır].
In English: “To wear a safety vest while running in the park is useful.” It feels more like general advice than a direct instruction.

Could you make this sentence into a direct recommendation with “should”?

Yes. In Turkish you can use the necessity suffix -malı/-meli on the verb:
Parkta koşarken güvenlik yeleği takmalısın.
Here takmalısın means “you should wear.” This addresses the listener directly, rather than stating a general fact.